Variable interval circuit breaking timer

ABSTRACT

A timer is provided for alternately opening and closing an electrical circuit in accordance with a preselected time interval determined by the surface contour and rate of rotation of a timer cam. A preselected resilient contact blade engages the timer cam surface and is moved thereby into and out of electrical contact. A selector cam having an array of cam surfaces selects those of a matching array of resilient contact blades which are to engage an array of rotating timer cam surfaces for chosen time intervals.

Inventor David Rosenberg Glen Cove, N.Y.

Appl. No. 830,078

Filed June 3, 1969 Patented Oct. 5, 1971 Assignee Pall Corporation GlenCove, N.Y.

Continuation-impart of application Ser. No. 643,083, June 2, 1967, nowPatent No. 3,447,479.

VARIABLE INTERVAL CIRCUIT BREAKING TIMER [50] Field of Search 200/38, 38A, 38 B, 38 C; 103/25; 222/70 [56] References Cited UNITED STATESPATENTS 2,351,828 6/1944 Marsh 103/25 3,465,110 9/1969 Marcel et al200/38 B 3,478,181 1 l/ 1969 Buckerridge et al 200/38 B PrimaryExaminerl-l. 0. Jones Attorney-lanes & Chapman ABSTRACT: A timer isprovided for alternately opening and closing an electrical circuit inaccordance with a preselected time interval determined by the surfacecontour and rate of rotation of a timer cam. A preselected resilientcontact blade 21 Claims 4 Drawing Figs engages the timer cam surface andis moved thereby into and US. Cl ..200/38 B, out of electrical contact.A selector cam having an array of 417/1 cam surfaces selects those of amatching array of resilient con- Int. Cl H0lh 7/08, tact blades whichare to engage an array of rotating timer cam H0lh 43/10 surfaces forchosen time intervals.

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SHEET 2 0F 2 CIRCUIT TIMER BREAKING LJ/" SWITCH POWR TIMER C PUMP MOTORMOTOR FIG. 4

VARIABLE INTERVAL CIRCUIT BREAKING TIMER This application is acontinuation-in-part of U.S. Pat. application Ser. No. 643,083, filedJune 2, i967 and now Pat. No. 3,447,479.

The mechanical clock has long been utilized for actuating mechanicaldevices. Originally, clocks or other similar timing devices wereutilized to either start or stop a particular piece of machinery at adesired time. As needs became more complex, specialized timers weredeveloped to allow the starting and stopping of equipment on asequential or interval basis. More sophisticated developments in thisarea include clocks with a choice of timing sequences, in which thesequence desired could be manually selected.

Timers of this type are useful for controlling many different types ofindustrial, commercial, medical and military equipment that requirevariable timing cycles for the many different operations that theyperform. For example, such a device is useful for selecting andcontrolling the pumping rate of a syringe pump.

The syringe pump is a device in which an electric motor in operativeconnection with a Scotch yoke, pivoted lever arm,

or cam reciprocates the plunger of a conventional syringe. By

utilizing a check valve in the influent and effluent lines leading toand from the syringe, the pump can be employed to continuouslyadminister doses of medicament to a patient. The rate at which themedicament is administered to the patient. The rate at which themedicament is administered to the patient is not necessarily, or shouldnot be, constant for all patients and all medicaments. If the motorwhich reciprocates the plunger of the syringe operates at a constantspeed, the motor must be alternately started and stopped at a desiredfrequency in order to effectively control or change the pumping rate ofthe syringe. This intermittent operation can be accomplished byutilizing a timer for opening and closing an electrical circuit; thetime intervals between actuations of the timer can be constant orvariable, and can be manually selected, according to the need.

Unfortunately, the available timers are complex and do not providesufficient time control to permit long time intervals betweenactuations. This prevents their use for controlling the pumping rate ofa syringe pump, since very low pumping output, wherein there is a longtime between each stroke, is often required.

Many timers utilize gear movements which are similar to the gearmovements of conventionalclocks. Timers have been made to actuate aswitch by providing a rotating arm which sequentially makes contact witha plurality of contact points located in the path of its rotary travel,to open and to close an electrical circuit. Other clock-type timingdevices utilize rotating cams, which move a cam follower into and out ofcontact with a contact point. The actuation rate of such timers can bevaried by changing the rotational speed of the arm or cam. This isaccomplished by relocating the position of several of the gears, anoperation which is similar to shifting gears in an automobiletransmission.

Due to their complexity, these timers can be diflicult to install anduse, and can be quite expensive, especially if their size is to be keptat a minimum, if high reliability is to be required, and a largeselection of actuation frequencies are to be made available. A timer tovariably control the actuation rate of some types of equipment,particularly a syringe pump for administering medicinal fluids topatients, must have high reliability, since human life is oftendependent upon it. Such a timer must also be compact, to allow itsinstallation within the pumping unit, to simplify the electricalcircuitry and increase its portability, and it must provide a sufficientnumber of different timing intervals, which can be easily and rapidlyselected by an operator.

In accordance with the present invention, a compact, inexpensive,reliable timer is provided, having a plurality of variable timingintervals for the opening and closing of an electrical circuit, andhaving means to manually or automatically select a desired timingsequence. Due to its versatility, the timer is well suited for use witha wide variety of different equipment, and in particular with a syringepump.

The timer of this invention comprises an array of resilient spaced timercontact blades having a portion movable between a first actuatingposition and a second nonactuating position; a rotatable selector camdisposed in operative juxtaposition to the array of contact blades, toselectively move said portion of at least one contact blade in the arraybetween the actuating and the nonactuating positions; an array ofelectrical contacts corresponding to the array of contact blades, e'achdisposed to be contacted by said portion of one of the blades when inits actuating position; and a motor-driven rotatable timer cam disposedin operative juxtaposition to the movable portions of the array of timercontact blades, and having an array of cam sections corresponding to thearray of contact blades, each section having a contoured surfacecorresponding to a different timing interval, to slidably engage theselected contact blade or blades disposed in the actuating position bythe selector cam for timed movement of the blade portions into and outof electrical contact with the corresponding contact, in accordance withthe contour of the timer cam surface.

The array of contact blades has at least two blades but can have anynumber of blades in excess of two. Each contact blade can be formed froman individual strip of a conductive resilient metallic material. Typicalmetals are copper, silver,

tin, alloys of copper such as beryllium-copper and bronze, al-

loys of silver and tin, and silver-, gold-, rhodium and platinumplatedmetals.

Any movable portion of the blade can be arranged to move into and outfrom engagement with the respective electrical contact. An end portionis easily moved or displaced, and is preferred. A portion intermediatethe ends can also be moved or displaced for this purpose. in the formercase, one of the ends of the blade is fixed, so that an intermediateportion can be moved or displaced with respect thereto.

A construction with a movable end can be as follows: One end of eachindividual blade can be mounted to a support base, to form the array ofspaced blades. The array of spaced contact blades can also be formedfrom a single sheet of a conductive resilient metal, and thus have acommon base. When formed from a single sheet, all of the contact bladesare in electrical connection with each other, and the common base can beconnected to a single terminal point, thereby simplifying the electricalcircuitry of the timer.

A construction with fixed ends takes the form of a single sheet withspaced slits corresponding to the width of the blades, and the sheet isbent in one direction of bow, so that the blades defined by the slitscan be moved to change the direction of bow, so as to move into or outfrom contact with the contact point. The actuating position can be at anunstable intermediate position to the extreme limit of the other stabledirection of bow, to which unstable intermediate position it is broughtand held by the selector cam, and it is then in contact with the timercam, on the opposite side, which allows it to move into the contactposition at predetermined intervals, and holds it away from contactposition at other intervals. When ever the selector cam is not in theactuating position, and the timer cam moves the blade to the unstableintermediate position, it snaps through to the original direction ofbow.

Another form with fixed ends has a plurality of flat strips with acentral portion of the strip slotted and cut to form a tongue that isbent in an S'shaped and is also fixed at each end. The S-portion of thetongue is adapted to change its direction of bow so as to move into orout of contact with the electrical contact point, as described above.

The array of contact blades is arranged so that the movable portion ofeach blade can be displaced to or from a normal position by the selectorcam and/or the timer cam, and can be resiliently returned to or from itsnormal position when released by the cams. Therefore, the blades can bein the actuating position when displaced by the cams or when at rest.depending upon the position of the cams and the electrical contacts withrespect to the blades.

The blades can also be rigid, and attached at one end to a resistentportion, which bends when it or the rigid portion is moved betweenactuating and nonactuating positions by the selector cam and/or thetimer cam. The blades can also be rigid, and pivotally mounted, as on ahinge or pivot pine, and biased towards the contact position, as by aspring or magnet, with a cooperating magnetic element affixed to theblade, such as a magnet or magnetically susceptible material.

The contact blades are preferably parallel fingers with movable endsextending from the base of the array toward the timer cam. The selectorcam can be disposed along the length of the blades between the base ofthe array and the timer cam to engage the blades for selective movementof each blade into or out from an actuating position. The selector camcan also be disposed at the movable ends of the contact blades and thetimer cam disposed along the length of the blades between their base andthe selector cam.

The array of contact blades can also be U-shaped wherein two sets ofparallel contact blade fingers extend from a common U-base to fonn the Uarms. This is the preferred shape, since the selector cam can beinterdigitally disposed between the contact blade fingers constitutingthe sides of the U, thus allowing one cam to selectively move two setsof contact blades, simultaneously or separately, without increasing thesize of the unit.

The selector cam is mounted rotatable to selectively move each contactblade finger individually in a pivotal direction about its mounting,between actuating and nonactuating positions. in the actuating position,as the term is used herein, the selected contact blade is either indirect electrical contact with a contact point, or positioned upon thesurface of the timer cam for movement into and out of electrical contactin accordance with the rotational movement of the timer cam. The contactbetween a given blade and its contact point can be continuous in everyposition of the timer cam, or sequential for timed actuation accordingto the position of the timer cam. A continuous electrical contact withone blade is required to provide current to the timer cam motor, and tothe syringe pump or other timed equipment, when their continuous ratherthan timed operation is desired. During continuous operation, theselector cam and the selected contact blade act merely as a switch toopen or close a circuit. During timed operation, the timer cam and theselected blade have this function.

The selector cam is formed with a plurality of cam sections, each havinga contoured surface which indirectly corresponds to a different timinginterval. Due to the position of the selector cam and the resiliency ofthe contact blades, at least one contact blade slidably engages thesurface of each selector cam section and is displaced by the cam uponits rotation, so that the selected rotational position of the camdetermines which blade will engage the timer cam for timed actuation,and which blade will make continuous electrical contact to providecurrent to the timer cam motor. The selector cam also holds those bladesnot required for the selected timing sequence in their nonactuatingposition, or permits them to return to their normal position, if that isthe nonactuating position.

The selector cam can be made of metal or plastic and can have any shapesuitable for rotational movement about an axis which is approximatelyperpendicular to the contact blades. Segments along the axis of the cameach have different surface contours, thereby forming a plurality of camsections. The selector cam can be formed either by permanently fasteninga plurality of cam segments to each other, or by forming differentcontours on the surface of a single cam. A single cam is preferred,since it is more easily and less expensively manufacture, and has higherstrength.

The contoured surface of the cam can be formed by utilizing eccentriccylindrical cam sections or elliptical cam sections having high pointswith respect to the rotational axis to displace the contact blades. Thecontours can also be either depressions, protrusions or steps, extendinglongitudinally across the cam surface to engage or release acorresponding portion of the contact blades. Protrusions on the camsurface can be raised ribs having rounded, flat or sharp peaks. Any

other shape of protrusion, such as a rounded bump formed on the surface,can also be employed, provided it can radially move a contact blade inthe required direction. When eccentric cylindrical or elliptical camsections, or protrusions upon a cam surface, are utilized to displacethe contact blades, a correspondingly formed section in the blade neednot be provided, inasmuch as the raised portion of the cam upon rotationwill come in contact with a flat portion of the blade, and thereby moveit from its nonnal position. Depressions formed in the cam surface canbe V-shaped or flat bottomed or rounded grooves, or a flat sectioncorresponding to a chord of a circle formed on the periphery of acylindrical cam. 1

When the selector cam is disposed along the length of the contact bladesbetween the base of the array and the timer cam, and grooves areutilized, it is preferred that the contact blades be formed with acorresponding protrusion to engage the grooves of the selector cam intheir normal position and be displaced by the cam surface when the camis rotated. If the selector cam is disposed at the movable end of thecontact blades, the tips of each blade can engage the grooves, andprotrusions on the blades are not required. When flat sections are usedon a cylindrical cam, protrusions need not be provided on the contactblade. If the selector cam is rotatably mounted so that the contactblades are released to their normal position when opposite the flatsection, simply rotating the selector cam so that the contact bladesslidably engage the curved portion will move the blades outwardly to thedesired position. The resiliency of the blades returns them to theirnormal position when this is permitted by the selector cam.

In the preferred embodiment of this invention, in which a U- shapedarray of contact blades is utilized, flat sections are provided on thesurface of a cylindrical selector cam to release the contact bladefingers on one side of the U. A single flat section is formed on eachcam section, and each flat section is disposed at a different angularposition upon the cam, thereby releasing a difi'erent contact blade ateach selected rotary position. The selector cam is interdigitallymounted of center with respect to the sides of the U-shaped contactblades, so that when the flat section on the surface of a cam section isopposite a contact blade, that particular blade will be released fromrestraint by the selector cam. The tip of the selected blade acts as acam follower to the rotating timer cam, and moves into and out ofelectrical contact according to the contour of the timer cam surface.Since the flat surfaces of the other cam sections are disposed atdifferent angles, and will not be opposite the remaining blades, theremaining contact blades will be displaced by the curved portion of thecam, and be held out from engagement with the timer cam.

At least one V-shaped notch or groove is formed in each selector camsection to release the contact blade fingers at the other side of the U.The blades on this side of the U are formed with a correspondingV-shaped protrusion which fits into corresponding notches of theselector cam as it is rotated. Rotational movement of the cam forces theprotrusions to move out of the groove, thereby displacing the bladesinto the actuating or nonactuating position. In the actuating-position,the contact blades provide contact for the timer cam motor or theequipment being controlled by the timer, but do not engage the timer camfor timed actuation.

The V-notches in one of the grooved sections of the selector cam alsoserve to lock the selector cam in a given position. The V-shapedprotrusion of one of the contact blades acts as a detent to lock in thegrooves, to maintain a given rotary position of the cam. Enough groovescan be provided to lock the cam in each of its rotary positions. Theforce exerted by the contact blade in resisting displacement by theselector cam from its normal position is sufficient to hold the blade inplace, and prevent undesired rotational movement of the selector cam.

The position of the protrusions, depressions or any other contour uponthe surface of the selector cam can be arranged so that any number ofblades will be displaced by the rotational movement of the cam. Thus,the selector cam can move one contact blade into continuous electricalcontact with a contact point at every position of the timer cam tocomplete the circuit to the timer cam motor, and at the same time canmove another blade into sliding engagement with the timer cam surface toalternately open and close another electric circuit in accordance with aselected time sequence. Furthermore, additional circuits may be openedand closed in accordance with other time sequences by contouring thesurface of other selector earn sections in the same or similar manner topermit the corresponding contact blade to simultaneously engage othersections of the timer cam. In this manner the timer of this inventioncan be used to provide timed control over a number of different devices.

The timer cam is mounted rotatably in operative juxtaposition to thearray of contact blades to slidably engage that particular contact bladeof the array which has been moved by the selector cam into the actuatingposition for timed operation, and thereby provides for movement of theselected-contact blade to open and close an electrical circuit. Thetimer cam can be disposed to engage the movable end of the selectedcontact blade or any other portion along its length. The contact bladein the position to which it is displaced by the selector cam is heldresiliently against the surface of the timer cam, thus permitting itsdisplacement into and out of electrical contact with a contact point inaccordance with the surface contour of the rotating timer cam.

The timer cam is formed with a plurality of cam sections disposed alongits length, each having a different contoured surface, to correspond tothe number of various timing intervals desired for each blade. As in thecase of the selector cam, the timer cam can have any suitable shape, andits surface contours can be depressions, protrusions or steps, extendinglongitudinally across each cam section. It is preferable that each timercam section adapted to engage the ends of the contact blades beapproximately cylindrical, and contain one or more steps or notchesspaced along its circumference. The tip of a selected contact bladesequentially enters each step or notch as it slidably rides along thesurface of the rotating cam. Electrical contacts are provided in closejuxtaposition to the blade, so that the blade will touch or other wiseengage the contact to complete the circuit, either when it enters thenotch, or when it is riding upon the curved surface. Similarly, whendisposed to engage a portion along the length of the contact blade, itis preferable that the timer cam surface have protrusions to displacethe selected contact blade into or out of electrical contact each timeit slidably engages a protrusion. Therefore, the circuit will be openedand closed as many times in one revolution of the timer cam as there arenotches or protrusions. The timer cam is designed to rotate at a fixedspeed, so that the timer interval between the opening and closing of thecircuit to provide timed control for electrical devices is directlydependent upon the number of notches or protrusions in each timer camsection providing the notches or protrusions are evenly spaced.

The selector cam and the timer cam are preferably both formed from anonconductive material, such as plastic or ceramic, but they can also beof metal if these cams are electrically isolated. Plastic materials,such as Delrin (polyoxymethylene) PPO and NORYL (polyphenylene oxide),nylon, polyvinyl chloride, polyethylene, polypropylene, polycarbonate,and polytetrafluoroethylene, are preferred, since they are inexpensive,readily formed into the desired shapes, and are sufficiently strong towithstand continuous use.

The drive for the timer cam is provided by means of a synchronous orother constant speed motor. The timer cam can be either directlyconnected to the motor shaft or can be indirectly connected by means ofa gearing system. The rotational speed of the timer cam determines thetype of connection between the motor and the cam. ln most cases, it willbe necessary to step down the speed of the motor by the utilization ofseveral gears. The utilization of these gears, however, has nodetrimental effect upon the reliability of the timer, inasmuch as theyare fixed in a permanent axial position, since the speed of the timercam is maintained at a constant rate.

A synchronous motor is not as suitable as an induction motor for thesame power output because it is more expensive, much heavier, and muchlarger in size. However, an induction motor is not as uniform inrotational speed, with applied load, as a synchronous motor. By using asynchronous motor to operate the timer cam, and the timer to operate aninduction motor, it is possible to impose upon the operation of theinduction motor the uniformity in operation of the synchronous motor.Moreover, with this arrangement it is possible to get very low effectiver.p m. from an induction motor by permitting it to go only 1 revolutionin a predetermined timer interval, and this is accomplished withoutspecial gearing or other expensive expedients.

The electrical contacts can be located at any point along the length ofthe contact blades, provided that they are sufficiently close to theblades to permit the completion of the electrical circuit upondisplacement of the blades by either the selector cam or the timer cam.The contacts can be positioned on either side of the contact blades, sothat the circuit will be made by the blades when they are displaced bythe cams, or when they are in their normal position. Individual contactpoints can be provided for each blade, or preferably a single conductivestrip can be provided to be contacted by several blades, thussimplifying the required wiring by reducing the number of connections.

The timer operation provided by a given selection of contact blades isobtained by rotating the selector cam to a position at which a blade ismoved into contact with a contact point to complete the circuit to thetimer cam motor, thus starting rotation of the timer cam for timedactuation, and another contact blade is simultaneously moved into aposition to ride upon the surface of a timer cam section. When thecontact points are so located that they are contacted by the blades intheir normal position, and a notched timer cam is utilized with thesurface of the cam holding the blade away from its normal position, eachtime the selected blade engages a notch in the time cam, its resiliencywill return it to its normal position, thus contacting the point tocomplete the circuit for timed operation. As the timer cam continues torotate, the blade will in due time leave the notch, and will bedisplaced by the timer cam surface, thereby breaking the circuit, untilthe blade engages the next notch. If a different timing interval isdesired, the selector cam is rotated to another position, in which adifferent blade will be moved into actuating position, to ride upon thesurface of another timer cam section having a different number and/orspacing of notches.

To simplify the selection and actuation of a particular timing interval,one end of the selector cam can be provided with a knob to allow manualrotation of the selector cam. A mark on the knob and a dial having adifferent designation for each position of the cam is also desirable toindicate the various timing intervals available in the several positionsof the selector cam. The timing interval can also be automaticallychanged by connecting one end of the selector cam to a motor or solenoidwhich will provide torque to turn the cam to another position. The motoror solenoid can be controlled by the timer of this invention to actuateupon the completion of a particular time cycle.

To turn off the controlled load operated according to the position ofthe blade riding on the timer cam, such as after one reciprocation of asyringe plunger by a syringe pump, it is desirable to provide anindependent switch to break the electrical circuit. If such a switch isused, the contact blades are used only to complete the circuit. Thecircuit breaking switch can be attached to the equipment beingcontrolled by the timer. A simple inexpensive normally closed switch,such as a snap action switch, can be actuated by, and held open by alever arm, can or any other mechanical component connected to andoperated by the equipment, each time the equipment completes itsoperational cycle, to break the circuit and cease operation. The timercam and the cyclic operation of the equipment must be so set that thetime of contact of the contact blade is less than the time required tocomplete one operation cycle, and the total time required for the timercam to rotate from one notch to the next must exceed the time for thecontrolled equipment to complete the cycle. The first can beaccomplished simply by forming the notches on the timer cam surface toensure that the duration of contact by the contact blade is quite short,and the second is obtained by suitably selecting the spacing of thenotches or the number of notches on the timer cam, and/or by therotational speed of the timer cam.

By wiring the timer and the switch in parallel, displacement of theblade from the contact point will not break the circuit, since theswitch is normally closed. Only when the lever arm actuates the switchat one end of the cycle will the circuit to the equipment be broken.Having ceased operation upon actuation of the switch, the lever arm ofthe equipment will hold the switch in the open position. The timer cam,however, con tinues to rotate at a constant speed, inasmuch as the timercam motor receives power from another circuit. When the blade falls intoanother notch upon the cam surface, it will again meet the contact pointand complete the circuit to the equipment. When the equipment beginsoperation, the lever arm will move away from the switch, permitting itto close, and thus repeating the cycle.

It is sometimes desirable for equipment to operate on a single cyclebasis, that is, where the equipment will complete one operational cycleand then automatically be stopped. This can be accomplished by utilizingthe normally closed circuit breaking switch set to open upon thecompletion of the operational cycle as discussed above, together with amanually operated normally open reset switch, which can be a simplepushbutton switch, or normally open snap acting switch, or the selectorcam above can be used as a reset switch, by tuming to continuousoperation to start the motor, allow enough time for the equipment toclear the circuit-breaking switch, and then turning the selector cam tothe off position. The motor will then stop when 1 cycle has beencompleted.

Since the timer of this invention is relatively small, it can be put inthe same housing as the equipment required timed operation. This greatlysimplifies the circuitry required, since all wiring will be internal,and many wires can be made common to several circuits. Therefore, whenthe timer is employed to control the pumping rate of a syringe pump, itis preferably to install both the timer and the drive for the syringe ina single housing.

The syringe pump-timer assembly of the invention comprises, incombination, a syringe having a fluid-pumping plunger reciprocablymovable therein, drive means including an electric motor operativelyassociated with the plunger by means of a Scotch yoke, cam, or eccentricdrive and a slotted arm, for reciprocably moving the plunger within thesyringe to draw fluid into the syringe and pump it out, and a timer inaccordance with this invention as described above having a plurality ofvariable timing intervals which can be manually selected, to open andclose an electrical circuit to the pump drive motor at the end of aselected time interval, to control the frequency at which the plunger isreciprocated, and thus the pumping rate of the fluid. The timer can beadapted to actuate the pump drive motor after selected time intervalsbetween each stroke of the syringe, thus providing any desired pumpoutput, from very low to high. The pump is intended to be operated witha check valve assembly in fluid connection with the syringe to allowfluid to be drawn into the syringe from an influent line and to bepumped therefrom via an effluent line by the plunger upon itsreciprocating movement.

In the preferred embodiment, an eccentric drive pin and slotted drivearm operatively connect the pump motor and syringe plunger. A normallyclosed circuit-breaking switch wired in parallel to the timer circuit isutilized to stop the pump motor at the end of each timed interval. Thecircuit breaking switch is mounted within the housing adjacent theslotted end of the arm. The switch is actuated by the arm to open thecircuit when the plunger of the syringe is at a selected position,preferably fully extended. The end of the plunger or any other suitablemeans can also be utilized to open the switch.

The syringe pump is controlled by manually turning a selector knob tothe desired timing interval. This rotates the selector cam of the timerto move a selected contact blade into position to complete the circuitto the timer cam motor and a second selected contact blade released intoposition to ride upon the surface of a rotating timer cam section. Whenthe tip of the second contact blade moves in response to the timer camsurface, to complete the circuit to the pump motor, the motor commencesoperation. As the drive arm begins to reciprocate the plunger of thesyringe, the switch closes and completes the parallel circuit. Prior tothe completion of one pumping stroke, the contact blade is moved out ofelectrical contact by the timer cam surface and opens that portion ofthe circuit. The pump, however, will continue to operate until theplunger returns to its original position, at which time the switch isopened. The cycle will be repeated each time the contact blade is movedinto electrical contact by the timer cam surface.

It is preferable that a timer comprising an array of U-shaped contactblades and a notched timer cam be utilized to control the pumping rateof the syringe pump. Since the U-shaped array provides for an increasednumber of circuits without increasing the size of the timer, such adesign allows a great amount of control over the pumping rate of thesyringe and yet permits a compact, reliable unit. By utilizing a notchedtimer cam the pumping rate is controlled by the number of notches in theselected timer cam section, there being a single stroke of the syringeplunger for each notch engaged by the contact blade. If the timer camrotates at l revolution per minute and has three equally spaced notches,the syringe plunger will begin a stroke every 20 seconds. It is, ofcourse, possible to space the notches on a particular cam sectionunequally, so that the operation of the syringe pump conforms to a timesequence having unequal intervals. For example, it may be advantageousto cycle the syringe three times in the first 15 seconds of operationand then cease operation for 45 seconds. Assuming that the timer cam isrotating at l r.p.m., this can be accomplished by positioning threenotches in the first quadrant of the timer cam section. The 1 rpm.rotational speed of the timer cam is by way of illustration only, and inon way limits the scope of its operation. By utilizing the proper gears,the timer cam can be made to rotate at any speed attainable.

The syringe pump timer assembly is lightweight, and compact. The timercam can be provided with a sufficient number of cam sections and contactblades to provide a wide range of various pump speeds, a reset switchcan be provided for single stroke operation, and a selector position canalso be provided wherein a contact blade is in continuous electricalcontact for continuous rather than sequential pump operation.

The timer of this invention and its utilization with a syringe pump arefurther explained by reference to the drawings in which:

FIG. 1 is an isometric view of the timer of this invention.

FIG. 2 is an isometric breakaway view of the preferred embodiment of thetimer.

FIG. 3 is a plan view of the syringe pump-timer assembly, showing apartial internal view of the timer and pump mechanism.

FIG. 4 is a schematic diagram of the electrical circuitry of the syringepump timer assembly of FIG. 2.

The timer of this invention shown in FIG. 1 comprises an array 1 of fourresilient contact blades 2, 3, 4, 5, formed from a sheet of electricallyconductive metal. The individually spaced contact blades, 2, 3, 4, 5extending from the common base 6, are radially movable at their freeends 7, 8, 9, 10 between actuating and nonactuating positions. Amanually rotatable selector cam 15 is disposed in operativejuxtaposition to the array of contact blades. Protrusions 1 la, 12a,13a, 14a and flat portions 11b, 12b, 13b are positioned in differentspaced locations on shaped cam sections 11, 12, l3, l4, opposite thecontact blades 2, 3, 4, and 5, to selectively move these contact bladesbetween their actuating and nonactuating positions. Conductive strips 16and 17 act as the electrical contacts, and are disposed to be contactedindependently by the conductive blades according to the position of theselector cam, to complete an electrical circuit to the timer cam motor(via blade only) and to the device operated by the timer (blades 2, 3and 4) at selected time intervals.

A timer cam 18 which is rotatably driven by an electric motor 19 isdisposed in operative juxtaposition to the movable ends 7, 8, 9 of thearray 1 of contact blades 2, 3, 4, and has cam sections 20, 21, and 22,which are opposite contact blades 2, 3, and 4, respectively. Each timercam section has a contoured surface with steps 23 which are spaced tocorrespond to different timing intervals. These surfaces slidably engagethe ends 7,, 8, 9 of a selected contact blade 2, 3 or 4, disposed in theactuating position by the selector cam 15, for timed movement into andout of electrical contact with the strip 17, in accordance with thespacing of steps 23 in the timer cam section.

The blade 5 has no corresponding timer cam section, but instead itactuates the electric circuit to the timer cam motor 19 when in contactwith the contact strip 16, which is when it is in the upper positionshown in the drawing. The high area 14a on selector cam section 14 isover a length of cam surface to put blade 5 in the actuating positionwhenever any of blades 2, 3, 4 is in the actuating position.

The common base 6 of the array 1 of contact blades provides a commonelectrical connection for all of the contact blades and thus simplifiesthe wiring of the timer by allowing the use of a single terminal point25 to connect all of the contact blades to the power resource 26.

The contact blades 2, 3, 4 in their normal position (to which theyalways strive to return when displaced therefrom) stand free above theflat portions 11b, 12b, 13b, of the selector cam, and have their tipsresting against the timer cam sections 20, 21, 22, respectively. Thehigh points 11a, 12a, 130, on the selector cam sections 11, 12, 13 areeach in different radial positions with respect to the contact blades,so that each contact blade will be lifted independently intononactuating position, and only one at a time will be opposite a fiatportion 1 1b, 12!), 13, so as to be in actuating position against thetimer cam sections 20, 21, 22. The blade 5 is displaced by a high area140 on the cam surface 14, to make continuous contact with strip 16 toprovide continuous electrical current to the timer cam motor 19. In theactuating position the blades 2, 3, 4 are not radially displaced by theselector cam and their movable ends 7, 8, 9 are permitted to slidablyengage the surface of the timer cam sections 20, 21, 22 for timedmovement into contact with strip 17. The timer cam section steps 23 areso spaced and shaped that the selected contact blade will spring intocontact with strip 17 each time the end of the blade is located at thebase of a step 23. The spacing between the steps plus the rate ofrotation of the timer cam determines the time interval for contact. Asthe timer cam 18 rotates, the contact blade is engaged by the camsurface and is moved out of contact with the contact strip 17. The bladethen rides on the surface of the cam. During the rotation of the camwhenever the blade reaches a step 23, the blade is released, and snapsinto contact with strip 17, thus providing for timed actuation of thecircuit between points A and B, in accordance with the spacing of thesteps 23 in the timer cam surface. Each timer cam section 20, 21, 22 hasa different number of steps, so that the time interval betweenactuations of the circuit will be different for each selected contactblade 2, 3, 4.

In the OFF position the blades 2, 3 and 4 are held out of contact withthe timer cams 20, 21, 22 by the selector cam high points 11 a, 12a, 13aof the cam sections 11, 12 and 13. The low point of the cam section 14at this time faces the blade 5 thereby permitting it to move out ofcontact with the strip 16.

in operation, the selector cam 15 is rotated to the desired position,which corresponds to a particular timing interval. This moves two of theselector blades 2, 3, 4 into a nonactuating position leaving one bladein its normal position, with its end resting on timer cam 18. Blade 5contacts strip 16 to provide continuous current for the timer cam motor19, and timed actuation for the circuit between points A and B. Forexample, in the position of the selector cam 15 shown in FIG. 1, contactblades 3, 4 are displaced by high points 120, 13a of cam sections l2,l3, and therefore are in their nonactuating position, while blade 2 isopposite flat portion 11b, is not displaced by section 11, and has itstip 7 slidably engaging the surface of timer cam section 20. Blade 5 isdisplaced by the high area 14a of selector cam section 14 and is in itsactuating position in contact with strip 16, thus providing continuouscurrent to the timer cam motor 19.

Timer cam section 20 has two steps 23 fonned in its surface. Therefore,as the timer cam rotates, contact blade 2 will make electrical contactwith terminal strip 17 twice in each revolution of the cam. Furtherrotation of the selector cam will displace blade 2 and individuallyallow any of remaining contact blades to move into its actuatingposition upon the respective timer cam section, to provide additionaltiming intervals.

If desired, blade 5 can be eliminated by adding another position toblades 2, 3, 4, and extending strip 16 so as to be contactable any ofblades 2, 3, 4 in the added position. There must then be two raisedportions, or three levels, of the corresponding selector cam sections11, 12, 13, the highest level raising blades 2, 3, 4 one at a time atdifferent positions of the selector cam into contact with contact strip16, so that one of blades 2, 3, 4, always actuates the timer motor whileone of the remaining blades is in normal actuating position againsttimer cam 18.

The embodiment of the timer shown in FIG. 2 is preferred for timedcontrol of a syringe pump, since it provides additional circuitconnections without appreciably increasing the size of the unit, ordecreasing its reliability. it comprises an array 30 of U-shaped contactblades to open and close an electrical circuit at the end of theselected timed interval. A rotatable selector cam 31 having cam sections32, 33 and 34 is interdigitally disposed between the sides of theU-shaped contact blades and in operation juxtaposition thereto, toselective move the contact blades away from their normal and actuatingpositions, into a nonactuating position. A motor driven rotatable timercam 35 having cam sections 36, 37 and 38 is positioned at the tips ofthe array of timer blades. Each cam section has a notched surface withthe notches 54 spaced differently to correspond to different timingintervals, to allow a I blade to contact the strip 39 when its tip restsin a notch, and

to slidably engage the tip of a selected contact blade for movement outof electrical contact with contact strip 39 whenever the tip contacts anonnotched portion on the timer cam surface. The number and spacing ofthe notches and the rate of rotation of the cam determine the timinginterval between contacts and thus actuation of the load.

The array 30 of contact blades is formed from a single sheet ofsliverand gold-plated beryllium-copper and has six spacedapart resilientfingers 40, 41, 42, 43, 44, 45, three on each side of the U. A singleelectric line 48 leading from the power source 49 to a common terminalpoint 47 provides electrical current to all six fingers. When in theirnormal actuating positions, the tips of contact blade fingers 40, 41 and42 on one side of the U engage the surface of the several segments 36,37, 38 of the timer cam 35, and provide for timed actuating of anelectrical circuit by movement into and out from contact with strip 39.Finger 43 on the near side of the U when in its actuating position makeselectrical contact with contact point 55 to provide continuous currentvia lines 52, 53 to the load, in this case, a syringe pump. Finger 45when in its actuating position closes the circuit to the timer cam motor57 by contacting point 46, and thus turns on the motor. Each of fingers43, 44, 45 is provided with a protrusion 43a, 44a, 45a. The protrusion440 on finger 44, which is shorter than the fingers 43 and 45, acts as adetent in combination with the notches 33b on the cam section 33 to holdthe selector cam in any selected position. Cam section 33 a notch 33bcorresponding to each rotary position of the cam, to lock the cam inplace in every rotary position.

A selector knob 50 is provided for manual rotation of the selector cam31 to each position. The torque exerted manually upon the knob 50 issufficient to displace the detent and move the cam to the desiredposition.

The protrusions 43a and 45a act as cam followers which, in combinationwith the selector cam sections 32 and 34 and the notches 32b and 34b,move the fingers into and out of actuating position. The notch 32b is ofsufficient depth and width so that the protrusion 43a fits looselytherein so that the finger 43 freely rests against the contact 55without interference by the cam section 32. Notch 34b is of the samedepth as notch 32b. This depth is also sufficient to permit the finger45 to move completely clear of the contact 46 so that the protrusion 45arests against the bottom of the notch 34b.

Flat sections 32a, 33a and 34a are formed on the surface of selector camsections 32, 33 and 34, respectively, to release the blades so that thecontact blade fingers 40, 41, 42 assume their normal positions, in whichthey do not contact the cam sections 32, 33, 34, and their tips slidealong timer cam segments 36, 37, 38. Each flat section is disposed at adifferent angular position upon the selector cam 31, thereby releasingindependently into an actuating position a different contact bladefinger at each selected rotary position of the cam. When the flatsection on the surface of a selector cam section is opposite andadjacent finger of the contact blade, that particular finger (eitherfinger 40, 41 or 42) will be in its normal actuating position with itstip riding upon the timer cam. In the position of the selector cam 31shown as illustrative in FIG. 2, the flat section 32a of cam section 32is opposite contact blade finger 40, thereby allowing the tip of finger40 to remain in its normal actuating position and ride upon the surfaceof timer cam section 36. Since the fiat sections 33a and 34a of selectorcam sections 33 and 34 are disposed at different angles, they will notbe opposite to finger 41 and 42. Therefore, these fingers will bedisplaced to their nonactuating positions, away from timer cam sections37 and 38 by the cylindrical surface of selector cam sections 33 and 34.

When released by the flat portions of the selector cam 31 to theiractuating positions, the tips of the contact blades 40, 41, 42, rideupon the surface of the corresponding timer cam section, in response tothe contour of which they move into and out of electrical contact withstrip 39. In the position shown, blade 40 rides upon the surface oftimer cam section 36, and moves into electrical contact with strip 39each time it engages a notch 54. Since there are notches on the surfaceof timer cam section 36, the circuit will be opened and closed 10 times,in one revolution of the timer cam.

The timer cam 35 is rotatably driven by a constant speed electric motor57, the speed of which is stepped down by gears 58 and 59. Selector camsection 34 determines the position of contact blade finger 45 andwhether the circuit via contact 46 and line 49 will be closed to powerthe timer cam motor 57. In the position shown, protrusion 45a of contactblade finger 45 is resting upon the cylindrical surface of the selectorcam section 34, thereby displacing the finger 45 into contact with 46,its actuating position, to complete the electric circuit to the timercam motor 57. When the protrusion 45a engages the groove 34b, finger 45is released to its normal position, thus breaking the circuit, andhalting the timer cam motor.

The timer cam motor is a low powered motor with a long life, and can beleft on continuously if desired. In this event, it can be poweredoutside the timer circuit, or, alternatively, contact finger 45 can bearranged to close contact 46 in every position of the selector cam 34.The selector cam 31 also determined which of contact blade fingers 40,41, 42, will engage the timer cam 35 to provide timed operation.

In the OFF position of the selector knob 50, none of the contact bladefingers meets any contact point. Thus, no power either timed orcontinuous is fed to the equipment via lines 52 and 53.

In position A of the selector knob 50, electric current can becontinually fed to a syringe pump via lines 52 and 53. Fingers 40, 41and 42 are all displaced by the selector cam 31 and do not engage thetimer cam 35. The protrusion 45a of finger 45 fits into the notch 34b ofselector cam section 34, so that finger 45 is in its nonactuatingposition, and does not make electrical contact with contact point 46,and thus no electrical power is fed to the timer cam motor. Protrusion43a of blade 43 fits into notch 32b of selector cam section 32, thusallowing blade 43 to move into its actuating position, and engagecontact terminal 55. Since point 55 is electrically connected to line52, this completes an electrical circuit which provides continuouscurrent to the load, such as a syringe pump.

In position B, as shown in FIG. 2, blade 40 is released, being oppositethe flat 32a on cam portion 32, thus allowing its tip to ride on thesurface of timer cam section 36, and be moved away from and intoelectrical contact with strip 39 for timed completion of the circuit tothe load, in accordance with its engagement of the notches 54. In thisposition, the tip of contact blade 45 is displaced by selector camsection 34 into its actuating position, to meet contact point 46, andprovide electrical power from source 26 to the timer cam motor 57, vialines 49 and 56. Blades 41, 42, 43 are held away from their actuatingpositions by selector cam sections 33, 34, and 32, respectively, anddetent 44a locks the selector cam in this position.

In position C, contact blade 42 is released into its actuating positionbeing opposite the flat section 34a of selector cam section 34. The tipof the blade 42 thereby rides upon the surface of timer cam section 38and is moved into and out of electrical contact with strip 39 each timeit engages a notch 54, which is three times per cam revolution. In thisposition also, contact blade 45 is in its actuating position. Blades 40,41, 43 are held away from their actuating positions by selector camsections 32 and 33, and detent 44a locks the selector cam in thisposition.

In position D, blade 41 is released into its actuating position, beingopposite the fiat section 33a of selector cam section 33, for timedcompletion of the load circuit once per revolution, when it engagesnotch 54 of timer cam section 37. In this position also, contact blade45 is in its actuating position. Blades 40, 42, 43 are held away fromtheir actuating positions by selector cam sections 32 and 34, and detent44a locks the selector cam in this position.

In FIG. 3, the preferred embodiment of the timer is in operativeconnection with a syringe pump, to control the pumping strokes thereof.Both the pumping drive mechanism and the timer are mounted within aplastic housing 60. The timer is essentially as described with relationto FIG. 2. A selector knob 50 is provided to manually rotate selectorcam 31 to individually displace an array 30 of U-shaped contact blades40, 41, 42, into position to ride upon the surface of timer cam 35, andthereby provide timed operation of the syringe pump. Blade 43 providescontinuous operation of the pump. The pump comprises a motor drive wheel64, and a slotted arm 61 to reciprocate the plunger 62 of syringe 70.The arm 61 is pivotally mounted to the housing 60 by means of a pin 63.A slot 69 is provided in one end of the arm 61 so that it may beslidably connected by means of eccentric pin 68 to the drive wheel 64. Aslot 73 is formed at the other end of arm 61 to engage the flange 62a ofplunger 62. A nonnally closed snap acting switch 72 wired in parallelwith the timer is mounted within the housing 60 in close juxtapositionto the end of the arm 61 connected to the drive wheel. When the plunger62 reaches the bottom of the stroke, the arm 61 contacts the switch 72,causing it to actuate and open the parallel circuit to the pump motor.By choosing timed intervals that are always longer than the timenecessary for the pump to make one stroke, the switch 72 will always bein the open position when the timer contacts close. A standard electricplug 65 and a wire 66 are used to connect the syringe pump-timerassembly to an electrical outlet.

In operation, the selector knob 50 is rotated to the desired timingsequence, selected from those represented by the letters A, B, c, and D,which correspond to the different cyclic frequencies of the pump. Therotational movement of the knob 50 in turn rotates selector cam 31. Theselector cam 31 moves the selected contact blade (Position A, 43,Position B, 40, Position C, 42, Position D, 41) into its actuatingposition. In position A, blade 43 is in contact with point 55, and givescontinuous pump operation; blade 45 is in a nonactuating position. Whenblades 40, 41, 42 engage the corresponding grooved segment 36, 37, 38 ofthe timer cam 35, for timed cycling of the syringe pump, the contactblade 45 is moved into its actuating position, to complete the circuitto the timer cam motor. Each time the tip of a selected contact bladeengages a groove in the surface of the timer cam 35, it is released intocontact with contact strip 39, to complete the electric circuit to thepump motor.

As the pump motor begins its operation, drive wheel 64 rotates, causingarm 61 to pivot about point 63. The movement of the arm reciprocate-sthe plunger 62 of the syringe 70, thus drawing in fluid through thecheck valve assembly 71 from fluid line 74 during the downstroke, andpumping fluid into fluid line 75 via the check valve assembly during theupstroke. As the timer cam 35 continues to rotate, the contact bladeriding thereupon will be forced out of contact with strip 39 when itleaves the groove. This, however, does not stop the operation of thepump, since switch 72 which is in a parallel circuit is normally closed.When the plunger 62 reaches the bottom of its stroke, the end of the arm61 will actuate switch 72, thus stopping the flow of current to the pumpmotor, and halting its operation. As the timer cam 35 continues torotate, the selected contact blade will again engage a notch 54 in thesurface of the timer cam 35, and come in contact with contact strip 39,to again feed current to the pump motor, and begin its operation. Whenthe arm 61 moves out of contact with the switch 72, the switchautomatically closes.

Since switch 72 is used to break the circuit and the contact blades andpoints are used only to complete the circuit, the life of the contactblades and points will be appreciably greater than if they were used toboth open and close the circuit. In addition, the use of switch 72 tostop the pump ensures that the plunger 62 will be at the bottom of itsstroke at the beginning and end of each cycle. In this manner, thesyringe will be filled with fluid at the start of each pumping stroke,and will immediately pump fluid into fluid line 75 upon movement of theplunger.

In FIG. 4, the circuitry of the syringe pump-timer assembly of H6. 3 isshown. It can be seen in this schematic diagram that both the switch andthe timer are in parallel with respect to the pump motor. Therefore, ifeither is closed, the pump will be in operation. This allows bothcontinuous operation of the pump and timed operation, in accordance withthe selected position of the timer.

When continuous pumping is desired, the timer motor is not operating andcurrent is fed directly through the contact blades via a contact pointto the pump motor. Although the arm of the pump will open the switch atthe end of each stroke, this will not cease the pumping operation,inasmuch as current will still be fed via the cam operated contactblade. When timed operation is desired, the rotating timer cam displacesthe contact blade away from the contact point thus breaking the timercircuit to the pump motor. The switch, however, is normally closed sothat the pump will continue its operation until the arm actuates theswitch, at which point both parallel circuits will be opened and nocurrent will flow to the pump motor. When a contact blade again is movedinto position to complete the circuit by the timer cam, the operationcycle of the pump will repeat.

Having regard to the foregoing disclosure, the following is claimed asthe inventive and patentable embodiments thereof.

1. A timer for alternately opening and closing an electrical circuit inaccordance with any of a number of preselected timer intervals,comprising an array of conductive spaced timing contact blades having aportion movable between a first actuating and a second nonactuatingposition; a rotatable selector cam disposed in operative juxtapositionto the array of contact blades, and having an array of cam sections,each section having a contoured surface to selectively move at least onecontact blade in the array between the actuating and nonactuatingpositions; an array of electrical contacts corresponding to the array ofcontact timing blades and disposed to be contacted by the blades when inthe actuating position; and a motor-driven rotatable timer cam disposedin operative juxtaposition to the movable array of timing contactblades, and having an array of cam sections corresponding to the arrayof timing contact blades, each section having a contoured surfacecorresponding to a different timing interval and at least two sectionshaving differently contoured cam surfaces, to engage any selectedcontact blade disposed in the actuating position by the selector cam fortimed movement into and out of electrical contact with the correspondingmembers of the array of electrical contacts in accordance with thecontoured cam surface and rotational speed of the corresponding timercam section.

2. A timer in accordance with claim 1, in which the array of timingcontact blades comprises a plurality of thin flat parallel fingers inelectrical connection with each other, and extending from a common basewith one end movable between actuating and nonactuating positions.

3. A timer in accordance with claim 1, in which the selector camcomprises a plurality of cam sections, each having a different surfacecontour, and adapted to slidably engage and selectively move the contactblades between actuating and nonactuating positions.

4. A timer in accordance with claim 1, in which the contoured surface ofthe selector cam has high points which displace the contact blades formovement into an actuating or nonactuating position upon engagementtherewith.

5. A timer in accordance with claim 1 including a normally closedcircuit breaking switch connected in parallel to the timer circuit sothat both the timer circuit and the switch circuit must be open for theload circuit to be open.

6. A timer in accordance with claim 1, in which the contoured surfacesof the timer cam sections have at least one notch, and are adapted topermit movement of the selected contact blade into or out of electricalcontact with an electrical contact, upon its entering a notch.

7. A timer in accordance with claim 6, in which each timer cam sectionhas a different number of notches to provide different timing intervals.

8. A timer in accordance with claim 1, in which the array of contactblades is U-shaped, a omprises two parallel sets of thin flat fingers inelectrical contact with each other, and extending from a common U-baseto form the U-arms.

9. A timer in accordance with claim 8, in which the selector cam isinterdigitally disposed between the U-arms, to selectively moveindividual contact blades in both U-arms into an actuating ornonactuating position.

10. A timer for alternately opening and closing an electrical circuit inaccordance with any of a number of preselected intervals, comprising anarray of U-shaped timing contact blades having two sets of conductiveparallel fingers in electrical connection with each other, and extendingfrom a common U- base to form U-arms having resilient ends which aremovable relative to the U-base between an actuating and a nonactuatingposition; an array of electrical contacts corresponding to the array oftiming contact blades and disposed to be contacted by the blades when inthe actuation position; a rotatable selector cam interdigitally disposedbetween the U-arms of the array of contact blades, comprising ofplurality of cam sections, each having a different surface contour andadapted to engage and selectively move a finger in one U-arm of thetiming blades from a nonactuating to a first actuating position with anelectrical contact, and a finger in the other U-arm from a nonactuatingto a second actuating position for timed movement into and out ofelectrical contact with an electrical contact point; and a motor-drivenconstant speed rotatable timer cam disposed in operative juxtapositionto the movable ends of the sets of fingers, and having an array of camsections corresponding to the timing contact blades forming one U- oneelectrical contact and a contact blade adapted to continuously close thecircuit including the controlled load.

12. A syringe pump and timer combination having low output and adaptedto pump at variable rates with time intervals between each strokecomprising, in combination, a syringe having a fluid pumping plungerreciprocably movable therein; drive means including an electric motoroperatively associated with the plunger for reciprocally moving theplunger within the syringe to draw fluid into the syringe and pump itout; a check valve assembly in fluid connection with the syringe toallow fluid to be drawn into and pumped from the syringe by the plungerupon its reciprocating movement; and a timer having a plurality ofvariable timing intervals, which can be manually selected, to open andclose the electrical circuit to the pump drive means at the end of aselected time interval to control the frequency at which the plunger isreciprocated, and thus the pumping rate of the fluid; the timercomprises an array of conductive spaced timing contact blades having aportion movable between a first actuating and a second nonactuatingposition; a rotatable selector cam disposed in juxtaposition to thearray of contact blades, and having an array of cam sections, eachsection having a contoured surface to selectively move at least onecontact blade in the array between the actuating and nonactuatingpositions; an array of electrical contacts corresponding to the array ofcontact timing blades and disposed to be contacted by the blades when inthe actuating position; and a motor driven rotatable timer cam disposedin operative juxtaposition to the movable array of timing contact bladesand having an array of cam sections corresponding to the array of timingcontact blades, each section having a contoured surface corresponding toa different timing interval, and at least two sections havingdifi'erently contoured cam surfaces, to engage the selected timingcontact blade disposed in the actuating position by the selector cam fortimed movement into and out of electrical contact with the correspondingmembers of the array of electrical contacts in accordance with thecontoured cam surface and rotational speed of the corresponding timercam section.

13. A syringe pump and timer combination in accordance with claim 12, inwhich the array of contact blades comprises a plurality of thin flatparallel fingers in electrical connection with each other, and extendingfrom a common base with one end movable between actuating andnonactuating positions.

14. A syringe pump and timer combinations in accordance with claim 12,in which the selector cam comprises a plurality of cam sections, eachhaving a different surface contour and adapted to slidably engage andselectively move the contact blades between actuating and nonactuatingpositions.

15. A syringe pump and timer combination having low output and adaptedto pump at variable rates with time intervals between each strokecomprising, in combination, a syringe having a fluid pumping plungerreciprocably movable therein; drive means including an electric motoroperatively associated with the plunger for reciprocably moving theplunger within the syringe to draw fluid into the syringe and pump itout; and a timer having a plurality of variable timing intervals which Lcan be manually selected, to open and close the electrical circuit tothe pump drive means at the end of a selected time interval to controlthe frequency at which the plunger is reciprocated, and thus the pumpingrate of the fluid; the timer comprises an array of U-shaped contacttiming blades having two sets of conductive parallel fingers inelectrical connection with each other, and extending from a commonU-base to form U arms having resilient ends which are movable relativeto the U-between between an actuating and a nonactuating position; anarray of electrical contacts corresponding to the array of timingcontact blades and disposed to be contacted by the blades when in theactuating position; a rotatable selector cam interdigitally disposedbetween the U-arms of the array of contact blades, comprising aplurality move a finger in one U- arm of the timing contact from anonactuating to a first actuating position with an electrical contact,and finger in the other U-arm from a nonactuating to a second actuatingposition for timed movement into and out of electrical contact with anelectrical contact; and a motor driven constant speed rotatable timercam disposed in operative juxtaposition to the movable ends of the setsof contact fingers, and having an array of cam sections corresponding tothe timing blades forming one U-arm of the array, each section having acontoured surface corresponding to a different timing interval to engagethe end of the selected finger disposed in the second actuating positionby the selector cam for timed movement into and out of electricalcontact with an electrical contact, in accordance with the contour ofthe timer cam surface.

16. A syringe pump and timer combination in accordance with claim 15, inwhich the pump drive means and the timer are mounted within a singlehousing; and a knob for manual selection of a desired timing sequence isattached to the selector cam and rotatably disposed on the exterior ofthe housing.

17. A syringe pump and timer combination in accordance with claim 15, inwhich the pump drive means comprises a drive wheel operatively connectedfor rotational movement to the pump motor; a slotted pivotally mounteddrive arm adapted to engage the syringe plunger for reciprocal movementthereof; and a pin eccentrically mounted on the drive wheel to slidablyengage the slotted portion of the drive arm to provide for itsreciprocable movement in accordance with the rotational movement of thedrive wheel.

18. A syringe pump and timer combination in accordance with claim 17, inwhich the selected contact blade moves into electrical contact tocomplete the circuit to the pump motor at the beginning of each timedpumping stroke; and a normally closed circuit breaking switch adaptedfor actuation by the pump mechanism at the end of each stroke to breakthe circuit to cease the pumping operation.

19. A syringe pump and timer combination in accordance with claim 18, inwhich the circuit breaking switch and the timer circuit are wired inparallel, thus requiring both to be open in order to break the circuit.

20. A syringe pump and timer combination in accordance with claim 15,having means for single strike operation, which comprises a normallyopen manually operable reset switch to complete the circuit to the pumpmotor when the timer is not in use; and a normally closed circuitbreaking switch adapted for actuation by the pump drive means at the endof a single stroke of the plunger to break the circuit and ceaseoperation.

21. A timer in accordance with claim 6, in which each timer cam sectionhas a different spacing of notches to provide different timingintervals.

mg? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,610,848 Dated Q mh 5 19 Inventor(s) Qgvid Rosenberg It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1,1ine 25 & 26 "The rate at which the medicament is administeredto the patient." should be deleted.

Column 2 line 62 "S-shaped" should be --S-shape-- Column 2 line 75resistent"should be--r,esilient-- Column S line 3 "pine" should be--pin-Column S line 66 "manufacture" should bemanufactured-- Column 4 line 38"of" should be --off-- Column 6 line l0 "r.p. I m" should be-r.p.m.--

Column 6 1ine69 "can" should be--cam-- Column 8,1ine 41 "on" shouldbeno-- Column 9,-line 30 "resource"should besource- Column 10,1ine 22after "tactable" add--by-- ,olumn 10, line 38 '1 "operation "should be--operative-- Column l0,line 54 "sliver" should be-silver-- Column 11,line 26 "and' should be--a.n-

Column 11,line 6'7 "determined" should be -determines- Column 12,1ine 74"c" should be -C- Column 14,lin e l "a omprises"sl1ould be- -andcomprises-- Column 16,1ine55 "strike" should be -str0ke-- Signed andsealed this 18th day of July 1972.

(SEAL) Attest:

' 1mm E WARD M.F'I.ETCHER JR. ROBERT GOTTSC AitestingfifficeCommissioner of Patents

1. A timer for alternately opening and closing an electrical circuit inaccordance with any of a number of preselected timer intervals,comprising an array of conductive spaced timing contact blades having aportion movable between a first actuating and a second nonactuatingposition; a rotatable selector cam disposed in operative juxtapositionto the array of contact blades, and having an array of cam sections,each section having a contoured surface to selectively move at least onecontact blade in the array between the actuating and nonactuatingpositions; an array of electrical contacts corresponding to the array ofcontact timing blades and disposed to be contacted by the blades when inthe actuating position; and a motor-driven rotatable timer cam disposedin operative juxtaposition to the movable array of timing contactblades, and having an array of cam sections corresponding to the arrayof timing contact blades, each section having a contoured surfacecorresponding to a different timing interval and at least two sectionshaving differently contoured cam surfaces, to engage any selectedcontact blade disposed in the actuating position by the selector cam fortimed movement into and out of electrical contact with the correspondingmembers of the array of electrical contacts in accordance with thecontoured cam surface and rotational speed of the corresponding timercam section.
 2. A timer in accordance with claim 1, in which the arrayof timing contact blades comprises a plurality of thin flat parallelfingers in electrical connection with each other, and extending from acommon base with one end movable between actuating and nonactuatingpositions.
 3. A timer in accordance with claim 1, in which the selectorcam comprises a plurality of cam sections, each having a differentsurface contour, and adapted to slidably engage and selectively move thecontact blades between actuating and nonactuating positions.
 4. A timerin accordance with claim 1, in which the contoured surface of theselector cam has high points which displace the contact blades formovement into an actuating or nonactuating position upon engagementtherewith.
 5. A timer in accordance with claim 1 including a normallyclosed circuit breaking switch connected in parallel to the timercircuit so that both the timer circuit and the switch circuit must beopen for the load circuit to be open.
 6. A timer in accordance withclaim 1, in which the contoured sUrfaces of the timer cam sections haveat least one notch, and are adapted to permit movement of the selectedcontact blade into or out of electrical contact with an electricalcontact, upon its entering a notch.
 7. A timer in accordance with claim6, in which each timer cam section has a different number of notches toprovide different timing intervals.
 8. A timer in accordance with claim1, in which the array of contact blades is U-shaped, acomprises twoparallel sets of thin flat fingers in electrical contact with eachother, and extending from a common U-base to form the U-arms.
 9. A timerin accordance with claim 8, in which the selector cam is interdigitallydisposed between the U-arms, to selectively move individual contactblades in both U-arms into an actuating or nonactuating position.
 10. Atimer for alternately opening and closing an electrical circuit inaccordance with any of a number of preselected intervals, comprising anarray of U-shaped timing contact blades having two sets of conductiveparallel fingers in electrical connection with each other, and extendingfrom a common U-base to form U-arms having resilient ends which aremovable relative to the U-base between an actuating and a nonactuatingposition; an array of electrical contacts corresponding to the array oftiming contact blades and disposed to be contacted by the blades when inthe actuation position; a rotatable selector cam interdigitally disposedbetween the U-arms of the array of contact blades, comprising ofplurality of cam sections, each having a different surface contour andadapted to engage and selectively move a finger in one U-arm of thetiming blades from a nonactuating to a first actuating position with anelectrical contact, and a finger in the other U-arm from a nonactuatingto a second actuating position for timed movement into and out ofelectrical contact with an electrical contact point; and a motor-drivenconstant speed rotatable timer cam disposed in operative juxtapositionto the movable ends of the sets of fingers, and having an array of camsections corresponding to the timing contact blades forming one U-arm ofthe array, each section having a contoured surface corresponding to adifferent timing interval to engage the end of the selected fingerdisposed in the second actuating position by the selector cam for timedmovement into and out of electrical contact with an electrical contact,in accordance with the contour of the timer cam surface.
 11. A timer inaccordance with claim 10, including at least one electrical contact anda contact blade adapted to continuously close the circuit including thecontrolled load.
 12. A syringe pump and timer combination having lowoutput and adapted to pump at variable rates with time intervals betweeneach stroke comprising, in combination, a syringe having a fluid pumpingplunger reciprocably movable therein; drive means including an electricmotor operatively associated with the plunger for reciprocally movingthe plunger within the syringe to draw fluid into the syringe and pumpit out; a check valve assembly in fluid connection with the syringe toallow fluid to be drawn into and pumped from the syringe by the plungerupon its reciprocating movement; and a timer having a plurality ofvariable timing intervals, which can be manually selected, to open andclose the electrical circuit to the pump drive means at the end of aselected time interval to control the frequency at which the plunger isreciprocated, and thus the pumping rate of the fluid; the timercomprises an array of conductive spaced timing contact blades having aportion movable between a first actuating and a second nonactuatingposition; a rotatable selector cam disposed in juxtaposition to thearray of contact blades, and having an array of cam sections, eachsection having a contoured surface to selectively move at least onecontact blade in the array between the actuating and nonactuatingpositions; an array of Electrical contacts corresponding to the array ofcontact timing blades and disposed to be contacted by the blades when inthe actuating position; and a motor driven rotatable timer cam disposedin operative juxtaposition to the movable array of timing contact bladesand having an array of cam sections corresponding to the array of timingcontact blades, each section having a contoured surface corresponding toa different timing interval, and at least two sections havingdifferently contoured cam surfaces, to engage the selected timingcontact blade disposed in the actuating position by the selector cam fortimed movement into and out of electrical contact with the correspondingmembers of the array of electrical contacts in accordance with thecontoured cam surface and rotational speed of the corresponding timercam section.
 13. A syringe pump and timer combination in accordance withclaim 12, in which the array of contact blades comprises a plurality ofthin flat parallel fingers in electrical connection with each other, andextending from a common base with one end movable between actuating andnonactuating positions.
 14. A syringe pump and timer combinations inaccordance with claim 12, in which the selector cam comprises aplurality of cam sections, each having a different surface contour andadapted to slidably engage and selectively move the contact bladesbetween actuating and nonactuating positions.
 15. A syringe pump andtimer combination having low output and adapted to pump at variablerates with time intervals between each stroke comprising, incombination, a syringe having a fluid pumping plunger reciprocablymovable therein; drive means including an electric motor operativelyassociated with the plunger for reciprocably moving the plunger withinthe syringe to draw fluid into the syringe and pump it out; and a timerhaving a plurality of variable timing intervals which can be manuallyselected, to open and close the electrical circuit to the pump drivemeans at the end of a selected time interval to control the frequency atwhich the plunger is reciprocated, and thus the pumping rate of thefluid; the timer comprises an array of U-shaped contact timing bladeshaving two sets of conductive parallel fingers in electrical connectionwith each other, and extending from a common U-base to form U armshaving resilient ends which are movable relative to the U-betweenbetween an actuating and a nonactuating position; an array of electricalcontacts corresponding to the array of timing contact blades anddisposed to be contacted by the blades when in the actuating position; arotatable selector cam interdigitally disposed between the U-arms of thearray of contact blades, comprising a plurality move a finger in oneU-arm of the timing contact from a nonactuating to a first actuatingposition with an electrical contact, and finger in the other U-arm froma nonactuating to a second actuating position for timed movement intoand out of electrical contact with an electrical contact; and a motordriven constant speed rotatable timer cam disposed in operativejuxtaposition to the movable ends of the sets of contact fingers, andhaving an array of cam sections corresponding to the timing bladesforming one U-arm of the array, each section having a contoured surfacecorresponding to a different timing interval to engage the end of theselected finger disposed in the second actuating position by theselector cam for timed movement into and out of electrical contact withan electrical contact, in accordance with the contour of the timer camsurface.
 16. A syringe pump and timer combination in accordance withclaim 15, in which the pump drive means and the timer are mounted withina single housing; and a knob for manual selection of a desired timingsequence is attached to the selector cam and rotatably disposed on theexterior of the housing.
 17. A syringe pump and timer combination inaccordance with claim 15, in which the pump drive means Comprises adrive wheel operatively connected for rotational movement to the pumpmotor; a slotted pivotally mounted drive arm adapted to engage thesyringe plunger for reciprocal movement thereof; and a pin eccentricallymounted on the drive wheel to slidably engage the slotted portion of thedrive arm to provide for its reciprocable movement in accordance withthe rotational movement of the drive wheel.
 18. A syringe pump and timercombination in accordance with claim 17, in which the selected contactblade moves into electrical contact to complete the circuit to the pumpmotor at the beginning of each timed pumping stroke; and a normallyclosed circuit breaking switch adapted for actuation by the pumpmechanism at the end of each stroke to break the circuit to cease thepumping operation.
 19. A syringe pump and timer combination inaccordance with claim 18, in which the circuit breaking switch and thetimer circuit are wired in parallel, thus requiring both to be open inorder to break the circuit.
 20. A syringe pump and timer combination inaccordance with claim 15, having means for single strike operation,which comprises a normally open manually operable reset switch tocomplete the circuit to the pump motor when the timer is not in use; anda normally closed circuit breaking switch adapted for actuation by thepump drive means at the end of a single stroke of the plunger to breakthe circuit and cease operation.
 21. A timer in accordance with claim 6,in which each timer cam section has a different spacing of notches toprovide different timing intervals.